Servo system with fine and coarse adjustment



K. B. ELLER 2,561,654

SERVO SYSTEM WITH FINE AND COARSE ADJUSTMENT July 24, 1951 Original Filed Dec. 22, 1943 UUKDOU INVENTOR. Ke/c B. Eller. /Mn/ m u x 5 we 38.6w mm 2.0m

nun $5 30... numfiu $65: I i i muktimzit .551

H/S A TTO/PNEY Patented July 24, 1951 SERVO SYSTEM WITH FINE AND COARSE ADJUSTMENT Keith B. Eller, Tenaily, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. 1., a corporation of Delaware Continuation of application Serial No. 515,286, December 22, 1943. This application November 3, 1948, Serial No. 58,096

4 Claims. (Cl. 31830) 1 The present invention relates to remote control systems and particularly to a dual self-synchronous electro-mechanical servo control system for selective adjustment of an object to be angularly positioned with precision, and is the same as the invention disclosed in my abandoned application Serial No. 515,286, filed December 22, 1943, in which the following prior art was cited:

Mittag,j1,547,435, July 28, 1925; Edwards,

"1,985,982, January 1, 1935; Beyerle, 2,184,576,

which now provides improvements for such coarse and fine remote positioning of apparatus with a materially simplified discriminator network in place of the prior art systems, which utilized heavy transformers and complex networks to accomplish such results.

Also, in prior systems of this type wherein a slow synchronous self-induction system and a fast synchronous self-induction system are combined, such slow and fast synchronous systems must be kept in synchronism with respect to each other for precision adjustment of a controlled object. Accordingly, it is an object of the present invention to provide novel means for maintaining the slow and fast self-synchronous systems in synchronism with each other at a desired ratio for a prior coarse adjustment and a subsequent fine adjustment. 1

Another object is to provide a novel electromechanical remote control system, which is relatively much simpler in construction, easier to install and more durable than prior systems of this type.

The foregoing and other objects and advantages of the present invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing, wherein one embodiment of the invention is illustrated by way oi example. It is to be expressly understood, however, that the drawing is for purposes of illustration and description only and is not designed as a definition of the limits of the invention.

diagram of a system embodying the present invention.

Broadly, the present invention comprises dual self-synchronous transmitter and repeater systems. The two units of the dual transmitter and repeater may have any desirable ratio of operation with respect to each other such as 36:1, so as to provide a prior coarse adjustment system operating from a frequency cycle of one for each thirty-six cycles of the subsequently operated fine adjustment system which remains inoperative until the first system is near synchronism.

The rotors of the transmitters are geared together and the rotors of the repeaters are geared together at a ratio, such as 36:1, for example, so as to drive a follow-up mechanism connected to a polyphase motor through a discriminator unit adapted to provide priority of the coarse signal over the fine signal. When the coarse or slow and fine or fast signal voltages are present at the input of the discriminator network, and a suitable amplifier is connected to the output of the discriminator network, the discriminator circuit becomes energized so as to pass first only the coarse signal voltage and then only the fine signal voltage to drive a polyphase motor. The polyphase 'motor when thus energized drives first the coarse self-synchronous system to null and then drives the fine self-synchronous system to its null position, to thereby balance both systems at null in synchronism with the newly adjusted position of the transmitters.

Referring now to the drawing, the novel system of the invention may be powered'from a suitable alternating current source such as a crafts power supply represented by leads l0 and II shown connected to the rotors l 5 and l 6 which are responsive to any signal introducing means such, for example, as a gyro compass, or a master magnetic compass having a magnet rotatable or driven under the influence of the earth's magnetic field, or the like (not shown). Rotors I! and It are geared together by a mechanical arrangement having a ratio, such as 36:1, so that upon rotation, rotor it rotates 36 times as fast as rotor it. Such ratio of rotation providesa corresponding frequency ratio in the voltage signals induced in the windings of each stator II and is of the respective slow or coarse and fast or fine transmitters which, as shown, are of the Selsyn or Autosyn type. 1 x a The signal voltage so induced in stators i8 and i9 is introduced correspondingly into repeater stators 2| and 22. This signal voltage will then.

In the drawing, the single figure is a circuit through induction be introduced from slow ropeater stator 2| into slow repeater rotor 24 and from fast repeater stator 22 into fast repeater rotor 23. The receivers 2|, 24 and 22, 23 are also shown, by way of example, as being of the "Selsyn or "Autosyn type.

Connected to each rotor winding or coil 24 and 23 are transformers 34 and 33 having secondary windings 23 and 21. Winding 23 of transformer 34 supplies signal voltage from rotor 24 to the grids or plates of a rectifier tube 23 having its cathode or exciter filament connected to an output lead 33 grounded at point 3| and includes a resistor element 32 in one side of secondary winding 21 of transformer 33. Winding 23 is divided I d connected at the center to one side or negave end of winding or coil 21 and between the .latter and the resistor 32 and constitutes avoltage divider.

, The secondary winding 21 of the fast speed signal system has the other side thereof tapped by lead 33 to control grid 33 of a tube, such as twin triode-or phase shifter tube 33 of a discriminator network including a bias circuit or biasingmeans such as the resistor element or resistance 32 in one side of the secondary winding of the transformer 33. The circuit is completed to this side vo1 the tube 33 by connection to the'other end of I resistance 32, hich is connected to the output lead 33 and is therefore common to the conducting path of rectifier tube 23.

Rotor winding 24 is grounded at one side as in- "l dicated at point 43 and connected at the other side as indicated at point 4| through lead 42 to grid 44 of twin triode tube 33. The double triode or twin tetrode discriminator tube 33 is provided on each side of its exciter or repeater filaments 33 and 33 with the usual plates 43 and 41, which filaments 33 and 33 and plates 43 and 41 of tube 33 are connected to each other, respectively, and tube 33 is thus connected on its output side through leads 33 and 3| to the input side of amplifier 32, which may be of any suitable conventional type.

' The output of amplifier 32 is connected by leads 33 and 34 to each side of a winding 33, which is the second phase of a servomotor 33. The first phase of motor 33 comprises a winding 33 which has a phased excitation source which is supplied by the ship's supply lineor by any suitable generator system, (not shown) by leads 31 and 33 Rotor 3| of motor 33 is provided with take-off connections, namely shaft 32 connected, through gearing or the like to rotor 24, which is connected to rotor 23 by gearing or the like, represented diagrammatically by line 32 and line 31. Take off Shaft 33 from rotor 24 is adapted to drive any ob-' lect to be controlled to a position in synchronism with the transmitters of the two systems. The transmitter rotors l3 and II are also connected .as represented diagrammatically by line 33. The object to be controlled is thus driven to a position in synchronism first with the slow or coarse con-,

iii

. 4 spectively. As long as a signal voltage is present at secondary winding 23, the rectifier tube network automatically introduces a bias voltage, which appears across resistance element 32. This bias voltage is sufficiently high in value so that grid 33 is biased beyond its operating range, thus suppressing or cutting off the fast signal voltage,

into the amplifier.

While this bias voltage is present. grid 44 connected to rotor winding '24 receives voltage corresponding to the slow or coarse signal voltage and by virtue of amplifier 32 releases power to the second phase winding 33 of the servomotor 33. Power thus introduced into winding 33 operates the motor 33 to drive take-off gearing connections or like mechanism 32 and the object positioning take-oi! shaft 33, until the rotor 24 is rotated by mechanism 32 to an angle corresponding to the transmitter rotor l3. when such corresponding positions are reached by the rotors l3 and 24, the slow self-synchronous system is near synchronism and no signal voltage is present at grid 44 of tube 33.

Simultaneously there is no voltage induced in winding 23 of transformer 34 and consequently no cut-oil bias or fast signal suppressing bias voltage appears across element 32. For this condition of no cut-oil bias applied to grid 33 of tube 33, the fast or fine control portion of the system is operative and causes motor 33 to receive power controlled by the fast transmitter.

Having gained control of the power delivered to motor 33 the fast or fine control circuit will maintain the system as a whole in synchronism with the slow and fast self-synchronous systems in synchronism with each other at a desired ratio for a prior coarse adjustment and a subsequent fine adjustment.

As repeaterrotors 24 and 23 are geared together, sothat rotor 23 rotates 36 times as fast as rotor 24 and correspondingly fast transmitter rotor |3 also rotates 33 times as fast as slow transmitter rotor l3, the signal voltage has a fine sine curve adapted to pass zero for each cycle of rotation 36 times in one sine curve of rotation for the slow self-synchronous system.

Thus, when current stops at the null or'zero voltage position of the slow system the gear connection 32-31 to the fast system will permit a continued rotation, within limits, of the fast repeater rotor 23 driventhereby before its null or zero voltage position is reached.

For example, for about 5 degrees to either side of the slow system's synchronous position or null point. motor 33 will be energized by the fast system only for a finer positioning of the apparatus being'controlled. until the fast system has also reached its null point within this 5 degree cycleperiod. 1

Reversal of direction of torque to the induction motor 33 is accomplished by a reversal of phase of the output of the amplifier in accordance with a corresponding reversal of phase of the controlling voltage.

Thus, there is provided a novel dual selfsynchronous electromechanical selective remote or servo control and follow-up system, wherein a relatively slow or coarse self-synchronous remote control system connected to a fast or line self-synchronous remote control system is'oonnected through a novel discriminator network so that said slow system first operates to position an object to the exclusion of the fast system. until it reaches synchronism for its slow or coarse output with respect to the new position of the controlled object, whereupon the fast or fine system originally suppressed by the bias voltage from said coarse signal now proceeds to function and drives the object to a finer setting.

Although the present invention is described and illustrated in detail for only one embodiment thereof, it is to be expressly understood that the same is not limited thereto. For example, any desired ratio may be provided for between the coarse and fine systems and any reversible follow-up arrangement may be substituted for that shown in the drawing. Also various changes may be made in design and arrangement of the embodiment illustrated, as will now be apparent to those skilled in the art.

I claim:

1. In a remote control system comprising coarse and fine self-synchronous repeater systems each including a transmitter and a repeater connected in parallel in an electrical circuit having a source of signal power supply and having the rotors of the transmitters and the rotors of the repeaters connected together at a predetermined gear ratio, a pair of transformers connected to the repeater rotors to pass coarse and fine signal voltages introduced by said repeater systems, a rectifier connected to the secondary coil of the coarse repeater transformer and connected to one side of the secondary coil of the fine repeater transformer through a resistor, a twin triode discriminator tube having one grid connected to the other side of the latter secondary coil and another grid connected to the output of the coarse repeater, the secondary coil of the transformer of the coarse repeater having a divided voltage connection with the secondary coil of the fine repeater transformer between said side and said resistor, an amplifier having its input connected to the outputs of the tube, a polyphase motor having a fixed excitation source connected to one phase winding thereof and a second phase winding connected to the output of the amplifier, operative connections between the rotor'of the motor and the repeater rotors and an operative connection between the repeater rotors and the object to be adjusted, whereby when coarse and fine signal voltages are introduced by the repeater systems and passed by the transformers, said rectifier automatically introduces a bias voltage across the resistor of sufficiently high value to bias the grid connected to the secondary coil of the fine repeater transformer beyond its operating range to suppress the fine signal voltage into the amplifier and cause the motor to drive only the coarse repeater rotor by the coarse signal voltage to a position near synchronism with the rotor of the transmitter thereof and then cause the motor to be driven by the fine signal voltage before and after the coarse repeater system is deenergized and subsequently drive the fine repeater rotor until the same is in synchronism with the transmitter rotor thereof to a finer adjustment of the object than obtained by the coarse repeater rotor.

2. In a system for controlling movement at a remote point, the combination with means for introducing slow signal voltage having a wound transmitter rotor and a wound receiv er rotor and means for introducing a fast signal voltage having a wound transmitter rotor and a wound receiver rotor, each of said transmitter rotors being connected together so as to provide a ratio of one greater than that of the other, and each of said receiver rotors being connected together at a ratio similar to said transmitter rotors to provide annoua faster signal voltage in thewindingof ceiver rotor than in the-other, a polyphase motor having one phase thereof connected to a fixed source of power, a rectifying and discriminator network connected to theolltputsof' the receiver rotors, an amplifier connected to said outputs,

the other phase of the motor being connected to the output of said amplifier, drive means connecting said motor and said receiver rotors to drive the same in synchronism at the ratio' specified, and drive means connecting said motor to an object to be controlled at a remote point, said network including electric valve means for controlling said signal voltage in each of the receiver rotor windings, comprising a pair of transformers each having the primary winding thereof connected to an output of a repeater rotor, a thermionic tube having a pair of grids one of which is connected to the secondary winding of the transformer into which the fast signal voltage is introduced and the other connected to the secondary winding of the transformer into which the slow signal voltage is introduced, and a bias circuit network connected to the secondary winding of the slow signal voltage transformer and to one side of the secondary winding of the fast signal voltage transformer so that when said voltages are introduced into said secondary windings, said bias network feeds back a bias voltage through said fast signal voltage secondary winding of sufiiciently high value to suppress the fast signal voltage present therein and pass only slow signal voltage to the motor winding connected thereto to drive said motor until said slow signal voltage receiver rotor approaches the same angle of position as the transmitter rotor connected thereto to deenergize said slow receiver rotor to thereby cut out said bias voltage and pass only fine signal voltage to the motor to further drive the fast receiver rotor until the same is in the same angular position as the transmitter rotor connected thereto for a fine adjustment of said object.

3. In a system for controlling movement at a remote point, the combination with means for introducing slow signal voltage having a wound transmitter rotor and a wound receiver rotor ar means for introducing fast signal voltage havi.

a wound transmitter rotor and a wound receive rotor, signal power supply means connected to said transmitter rotors, each of said transmitter rotors being connected together to provide a ratio of one greater than the other and each of said receiver rotors being connected together at a ratio similar to the transmitter rotors to provide a faster signal voltage in the winding of one of the receiver rotors than in the other, a polyphase motor having one phase thereof connected to a fixed source of power, means connecting said motor and said receiver rotors together to correct for variations between the transmitter rotors and receiver rotors of each respective signal voltage introducing means, means connecting said motor and an object to be controlled at a remote point through the slow receiver rotor; of electric valve means for controlling said signal voltage in each of said receiver rotor windings comprising a pair of transformers each having the primary winding thereof connected to the output of a receiver rotor, secondary windings across each of said primary windings. a thermionic tube having a pair of grids one connected to said fast transformer secondary winding and the other connected to the output of said slow signal voltage rotor, a rectifier tube having plates connected to the sides said resistance of sufficiently high value to bias the grid connected to the fast transformer secondary winding beyond its operating range, cut ofi the fast signal voltage into the amplifier and cause the grids to receive and pass slow signal voltage to the amplifier and thence to the second phase of the motor to drive the latter and the slow receiver rotor and object to be controlled until the slow receiver rotor is near a position in synchronism with the position of its corresponding transmitter rotor and until said positions correspond to thereby cut off said slow signal voltage and pass only the fast signal voltage to drive said motor and said fast receiver rotor further until itsposition corresponds to the position of the fast transmitter rotor and correspondingly cause a finer adjustment of the object being controlled. 4. In a remote control system comprising coarse and fine self-synchronous repeater systems each including a transmitter and a repeater connected in an electrical circuit having a source of signal power supply and having the rotors of the transmitters and the rotors of the repeaters connected together at a predetermined gear ratio, a pair of transformers connected to the repeater rotors to pass coarse and fine signal voltages introduced by said repeater systems, a rectifier connected to the secondary coil of the coarse repeater transformer and to one side of the secondary coil of the fine repeater transformer through a resistor, a pair of electronic control devices. the input of one of said control devices being connected to the other side of the secondary coil of the fine repeater transformer and the input of said other electronic control device being connected to the output of the coarse repeater, the secondary coil of the coarse repeater transformer having a divided voltage connection with the secondary coil of the fine repeater transformer at the point where the secondary coil of the fine repeater transformer is connected to said resistor, a thermionic amplifier having its input connected to the outputs of said pair of electronic control devices, a polyphase motor having one phase thereof connected to a fixed excitation source and another phase connected to the output of said amplifier, and operative connections between the rotor of the motor, the repeater rotors and the object to be adjusted, whereby when coarse and fine signal voltages are introduced by the repeater systems and passed by the transformers, said rectifier automatically introduces a bias voltage across the resistor of sufficiently high value to bias the electronic control device connected to the secondary coil of the fine repeater transformer beyond its operating range to suppress the fine signal voltage and prevent it from being impressed on the amplifier, thereby causing the motor to drive the coarse repeater rotor by the coarse signal voltage to a position near synchronism with the rotor of the transmitter thereof and then causing the motor to be driven by the fine signal voltage before and after the coarse repeater system is deenergized and subsequently driving the fine repeater rotor until the same is in synchronism with the transmitter rotor thereof to a finer adjust ment of the object than obtained by the coarse repeater rotor.

KEITH B. ELLER.

REFERENCES orrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,547,435 Mittag July 28, 1925 1,985,982 Edwards Jan. 1, 1935 2,184,576 Beyerle Dec. 26. 1939 2,333,393 Ryder Nov. 2, 1943 2,409,970 Agins Oct. 22, 1946 

